The present invention relates to a semiconductor manufacturing device for performing wet etching only on one main surface of a semiconductor substrate, particularly a semiconductor manufacturing device suitable for producing a cantilever used for a probe of a scanning probe microscope.
In a scanning probe microscope represented by an atomic force microscope (AFM), a cantilever in which an exploring needle is formed at a free end of a beam portion is used as a scanning probe. In the configuration, because attraction or repulsion based on interatomic force appears between a surface of a sample and the exploring needle by scanning the exploring needle on the surface of the sample, a shape of the surface of the sample can be measured by detecting the interatomic force as a deflection of the cantilever.
FIGS. 7A to 7D are sectional views showing a method of processing the conventional cantilever as a specimen. First as shown in FIG. 7a, layered substrate 3 is prepared, which is layered with a SiO.sub.2 film 30, a silicon thin film 31 acting as a beam portion of the cantilever and an exploring needle, a SiO.sub.2 film 32 as an intermediate layer, a silicon substrate 33 acting as a supporting table of the cantilever, and a SiO.sub.2 film 34.
Next, a beam portion 31a of the cantilever and an exploring needle 31b are formed on a surface of the SiO.sub.2 film 34 by etching SiO.sub.2 film 30 into a proper shape so as to become a protecting film and by etching the silicon substrate 31 as the mask of the protecting film as shown in FIG. 7B. Moreover, SiO.sub.2 film 34 is properly etched so as to form a protecting film 34a, and surface &lt;100&gt; of the silicon substrate 33 is exposed.
Next, an end portion of layered substrate 3 is supported with a jig (etching holder) 50 sealed with an O-ring 51 for preventing inflow of liquid so that only the other main surface where said beam portion 31a and the exploring needle 31b of the layered substrate 3 is not formed is exposed by etching solution as shown in FIG. 7C. SiO.sub.2 film 32 exposes by etching the silicon substrate 33 as a mask of the protecting film 34 (34a) using anisotropic wet-etching.
For the etching solution, a potassium hydroxide (KOH) aqueous solution of 40 percentage by weight at 60 to 80.degree. C. a tetraalkylammonium hydroxide (TMAH) aqueous solution of 20 percentage by weight at 80 to 90.degree. C., and so on can be used. With these etching solutions, plane &lt;100&gt; of the silicon substrate 33 is etched much faster than plane &lt;111&gt; so that the protecting film 34a is not actually etched. Therefore, anisotropic wet-etching actually stops at plane &lt;111&gt; referenced with the end of the protecting film 34a. At the end, the extra SiO.sub.2 film 32 is removed as shown in FIG. 7D. By the above-described process, a cantilever is completed which has an exploring needle 31b at one end of the beam portion 31a and the other portion thereof is supported by a cantilever-like supporting table 60.
In the above-mentioned prior art, pressure increases corresponding to the depth of the etching solution at a processing plane of layered substrate 3 while pressure in the etching holder 50 is substantially at atmospheric pressure when the etching holder 50 holding the layered substrate 3 is sunk in the etching solution. Because of that, there has been problems that etching is performed unevenly and the substrate itself is broken by stress corresponding to a difference in pressure applied to both main surfaces.
When temperature of etching solution, gas in the etching holder 50 gradually expands thermally, and pressure applying to non-processing surface of the layered substrate 3 gradually increases. There has been a problem that stress toward reverse direction to the above-mentioned appears at the layered substrate 3 when pressure applied to the non-processing surface becomes higher than pressure applied to a processing surface corresponding to depth in the etching solution.
An object of the present invention is to provide a semiconductor manufacturing device substantially adjusting pressure applied to a non-processing surface to a processing surface of a semiconductor substrate in wet-etching in which the processing surface of the semiconductor substrate is exposed outside and the non-processing surface is sunk in etching solution so as to be sealed from outside preventing from inflow of the solution to solve the above-mentioned problem in the prior art.